GENETIC TYPE AND THE ENDOCRINES 27 



and disproportionately small. The pituitary and other glands 

 are almost uniformly modified. The genetic complex which 

 is associated with acromegalic growth and alteration of 

 the pituitary also seems to be associated in some cases with a 

 tendency towards loss of spinal neurones and a resulting 

 disappearance of certain muscles of the extremities. Such 

 tendencies may be readily imagined to progress as the race 

 becomes more homozygous for the mutant condition leading 

 to more extensive loss and modification of the posterior ex- 

 tremities and then spreading or becoming more generalized 

 to involve the anterior extremities as well. These changes 

 would qualify the animal for a floating or swimming existence 

 rather than for locomotion by dragging the heavy body on 

 land. 



Certain modified breeds of dogs show another peculiarity 

 suggesting the possibility of water living tendencies. The 

 slightly acromegalic giant Newfoundland dog is frequently 

 web-toed, and the toes of short legged achondroplasic dogs 

 such as the dachshund are often webbed almost to the tips. 

 Acromegaly and achondroplasia are not altogether mutually 

 exclusive reactions, but, as mentioned above for dogs, each 

 may occur in different parts of the same individual. And 

 this is also true for the marine mammals. Webbing of the 

 feet, a fin-like symptom in water birds as well as aquatic 

 mammals, does seem in many cases to be associated or cor- 

 related in some way with growth distortions such as achon- 

 droplasia, and likewise with a peculiar pituitary disturbance 

 in the breed. 



These introductory speculations and comparisons, which 

 are presented in an entirely theoretical manner, are intended 

 to indicate that the study of a highly diversified stock, such 

 as the domestic breeds of dogs, may furnish information 

 leading towards an understanding of the origin and develop- 

 ment of not only individual form and types but also of devia- 

 tions and changes away from an ancestral pattern which well 

 might give rise to new varieties and distinct species of 

 animals. Very probably, as has been pointed out by Sir 



